The present invention relates to a transmission system for four wheel drive, and more specifically to a transmission housing structure.
A published Japanese patent application No. 2001-146956 shows a bearing housing, such as transmission housing and differential carrier housing, formed with reinforcing ribs extending radially around a bearing portion for supporting a rotating shaft, to increase the rigidity with a smaller amount of material, and thereby to prevent deterioration of gear meshing due to deformation of the housing, and energy loss due to friction increase. A published international application WO 02/2514124 A2 (≈ Publication of Japanese language translation Pub. No. 2004-509298) shows a bearing housing having another rib structure.